Common CCTV DVR DIY Mistakes
This article will attempt to reveal some of the more common mistakes to avoid when creating your own CCTV DVR.
Many DIY'ers simply do not budget enough money for projects like this. When looking at cameras, look at the specs. A $200 security camera and a $50 security camera are going to be very different in terms of image quality and light response. Also look at CCTV DVR features. Places like Costco offer surveillance systems for under $500 but those surveillance systems don't have anywhere near the features of professional grade systems like Video Insight. Those systems can even be missing basic features like video motion detection. You may want to look for surveillance packages that combine everything you need to put a system together, including the CCTV DVR, security cameras, security camera lens's, mounts, power supplies, and cable. Packages like that can start at about $2000 and go up to $10,000 depending on the number of security cameras needed.
- Surveillance Camera Placement:
Surveillance camera placement is one of the most important factors in an effective surveillance camera system. Ask yourself the questions professionals do: How is the light coming in? How will this change at night? What am I trying to see? How do people move through the area? What kind of blind spots will there be? What kind of surveillance camera lens do I need to use? Do I need to use multiple surveillance cameras to cover this area? Would a side view be better for this then a straight on view?
- Selecting the right security cameras:
When looking at security cameras, understand what you are trying to do. Are you looking for license plate recognition? If so, then you need to select a camera lens that will allow the plate to be at least 1/3 of the image. This means that a surveillance camera with a wider field of view can not do license plate recognition. The same goes for facial recognition. If you are trying to cover a parking lot with a narrow entrance, you will have to use two surveillance cameras. Very wide entrances can make this very, very hard.
- Selecting the right camera lens:
Selecting the right camera lens is pretty easy. Note where you are going to place the camera and select the point where you want the best picture. Measure the distance from there to the camera. That is your focal distance. Then measure the width of the picture you want to see. Once you have these numbers you can feed them into a CCTV lens calculator. Looking at the F-stop will give an idea of how well that lens will work at night.
- Infrared or No?:
Infrared cameras are wonderful for covering areas of complete darkness. But many of the all-in-one camera/emitter units are fairly limited in range. This chart can help with deciding if you need to go the infrared route or not.
- Direct sunlight: 100,000 - 130,000 lux
- Full daylight, indirect sunlight: 10,000 - 20,000 lux
- Overcast day: 1,000 lux
- Indoor office: 200 - 400 lux
- Very dark day: 100 lux
- Twilight: 10 lux
- Deep twilight: 1 lux
- Full moon: 0.1 lux
- Quarter moon: 0.01 lux
- Moonless clear night sky: 0.001 lux
- Moonless overcast night sky: 0.0001 lux
- Focusing the video camera:
This is a simple and easy trick to help with focusing the video cameras. Use a BNC to RCA plug and a small television set to focus the video camera. The ideal time to focus the video cameras is in twilight because it will give the best compromise between the light and dark settings of the auto-iris lens.
- Cable types:
There are a few types of cable called RG-59. Copper vs. Aluminum sheet and 75% braid vs. 95% braid. For CCTV system work, you should always use copper shielding. Aluminum shielding is meant for modulated signals like cable and allows too much interference for CCTV systems. 75% braid and 95% braid measure how tightly and how much copper is used in the copper sheathing. 95% copper braided cable is more expensive but worth the extra expense. It is much more effective at preventing interference, and much more forgiving of mistakes. We only sell 95% braid copper shielded RG-59
- Cable runs and Ground loops:
Coax cable should be kept at least 12" away from any power lines and power conduits. The AC power creates a field of interference that will appear like snow on the screen. This can create havoc with motion detection. Ground loops can be caused by securing cameras to metal structures that have a different electrical ground then the power supply. This will cause bands to move through the screen. Solving this is a matter of eliminating contact between the cameras and the source of the ground.
- Sony Cameras:
Sony has a line of CCTV surveillance cameras, but all of them are clearly marked Sony. You will see a lot of sites offer "Sony" cameras when they don't say Sony on them. The reason for this is that Sony makes about 75% of the worlds CCD chips, which are used in everything from Camcorders to digital cameras to CCTV security cameras. The CCD is an important part of the security camera and has an impact on the resolution, but the electronics behind the CCD also have a big role in how good your image is.
- What determines how good my image is?:
How good your image is depends on quite a few things. It depends on how good your lens is, how well it is focused, what the resolution is, and how good the S/N (Signal to noise) ratio is. When looking at a camera, you generally want both the highest resolution and the highest S/N ratio you can find. The Signal to noise ratio is a Logarithmic scale so the difference between 46 dB and 48 dB is a rather large difference. If forced to select between a camera with a slightly lower resolution and a high S/N ratio or a camera with a higher resolution and lower S/N ratio, try to select the one with the better S/N ratio if you are doing longer (500 ft+) cable runs. For shorter runs going with the higher resolution is okay.
- How many FPS do I need?:
Many manufacturers and distributors will try to push their highest frame rate DVR's and Cards on you because those items have the best profit margins. But high frame rates may not be in your best interests from both a storage and budgetary perspective. For most applications 3 to 7 fps is fine. If your goal is to identify theft or vandals then 3 fps is almost always enough. The only time one should consider more then 15 fps is if you have to watch for sleight-of-hand like watching a register. The reason to avoid higher frame rates is that they take up more drive space, reducing the total storage time of the system. It can also divert budget away from selecting the right cameras which is far more important and more likely to generate usable evidence then a higher frame rate.
- Audio Recording:
Don't do it! In many states it is illegal, period. It does not matter if it is your home or other private property. The law only cares about if the people being recorded are aware that they are being recorded. A number of people tend to think "Well, I'll put it in anyway, it's not like someone is going to report me." The problem with that line of logic is that if you ever submit video as evidence to a court and you are in violation of your state's laws or federal laws, then you have just given proof to the courts that you also committed a crime. The best possible outcome is that the court throws out the recording and you don't go to jail. But if you can't use your recordings to help convict a person that has wronged you then what good was the money you spent?
As a general rule of thumb, anything you've seen done on television or in the Movies with video enhancement is simply not possible in the real world. You can't make data appear where there is none. There is no magic trick to make that work.
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